Canon PC920 - Transfer Roller Bias Control

CHAPTER 4 IMAGE FORMATION SYSTEM
COPYRIGHT © 1999 CANON INC. CANON PC800s/900s REV.0 AUG. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON) 4-8
Figure 4-105
Main
transformer
Transfer positive DC
bias generation circuit
Transfer positive DC bias ON signal
T_REV_ON*
T101
Transfer current detection signal
T_FW_S
Photo-
sensitive
drum
Transfer
charging
roller
Transfer DC bias
control signal
T_FW_DRV
Transfer bias voltage
detection signal
Transfer DC bias ON signal
T_FW_ON
High-voltage transformer
control signal
CLK32K
Transfer overcurrent detection signal
HV_LIMIT
+24V
T302
Transfer
high-voltage
transformer
Serial
communi-
cation
(Q101) (Q900)
Microprocessor Microprocessor
DC controller PCB Composite power supply PCB
Transfer bias
detection circuit
Transfer bias
control circuit
T_FEEDBACK
D. Controlling the Transfer Roller Bias
1. Outline
The circuit shown in Figure 4-105 is used to control the voltage applied to the transfer charging
roller, and has the following functions:
• Turning on and off the transfer bias.
• Controlling the transfer bias to a constant voltage.
• Correcting the transfer bias voltage level (ATVC)
• Switching the transfer bias polarity (cleaning bias)